1. Field of the Invention
This invention relates to a valve and lubricator assembly having particular utility on offshore locations in order to house a wire line or other tool while the shutoff valve and/or master or safety valve of the wellhead assembly are open. The present lubricator assembly when open functions as a pressure housing to permit a straight opening to the tubing therebelow or when closed, functions as a pressure barrier that allows installation of a wire line or other tools in a well in a safe manner.
2. Description of the Prior Art
During the completion, testing and/or workover of a subterranean well at an inland location, it may be necessary to run equipment such as a perforating gun or the like on a wire or electric line into the well when the well is under pressure. This is achieved by inserting the equipment into a length of production tubing above the christmas tree, the length of tubing being commonly referred to as a "lubricator". The lubricator section is isolated from the portion of the well therebelow by a valve or a series of readily accessable hand manipulated valves. On some inland locations, it may be necessary to extend the lubricator section as high as 60 feet into the air.
On offshore locations, where space is at a premium and valves are not readily accessable, an inland-type lubricator is not practical. For example, use of such an extended length of tubing may be hazardous when applied to an offshore well site utilizing a floating vessel thereabove. Relative motion between the floating vessel and the tubing string which is anchored in the well within the sea bed causes considerable difficutly in manipulation of manual valves.
Most offshore locations will utilize a riser pipe extending from the floating vessel to the ocean floor where it is connected to the uppermost portion of the blowout preventer stack. The riser functions as casing and provides a conduit for mud circulation and isolation of the well from the sea. Whenever the well is "live" or capable of flowing, there is usually tubing between the floating vessel and the blow out preventer stack. This tubing will be inside the riser, if a riser is used. This tubing section is available for use as a lubricator section for insertion therethrough of wire or electric line equipment if a valve is provided therebelow. Use of the riser pipe as the lubricator section will eliminate use of an extending lubricator section above the floating vessel and will thereby eliminate the hazards involved in such use.
In view of the fact that the lubricator assembly must contain the well pressure while the equipment is inserted therethrough for subsequent utilization in the well, it is necessary to control the well pressure below the lubricator assembly during this procedure. This is achieved by use of a valve assembly within the lubricator section. Some commercial and prior art lubricators contain normally open valve assemblies which permit the valve to automatically open if hydraulic control pressure is lost. Under certain conditions, if control pressure were lost, a blow out might result. Other lubricator valve assemblies contain normally closed valve assemblies which permit the valve to automatically close if hydraulic control pressure is lost. Normally, closed valves can close and sever the wire or other line if control pressure is lost, possibly damaging the valve and rendering it inoperable, thereby causing a blow out of the well. Moreover, each of these types of prior art valve assemblies are somewhat disadvantageous in that they are not fail-safe, that is, the open or closed position of the valve is not affected by loss of control pressure.
The present lubricator valve assembly overcomes many of the disadvantages of the prior art apparatuses by providing a mechanism which utilizes a combination of pressure means to activate the valve element. Additionally, the present lubricator assembly provides means for locking the valve manipulating mechanism when the valve element is in closed position. The present lubricator and valve assembly are not automatically manipulated when control pressure is lost, which results in a fail-safe valve assembly. Moreover, the present lubricator assembly also provides a means for both reducing metallic friction on the ball valve surfaces during the opening and closing manipulating steps as well as providing a metal-to-metal seal when pressuring above the ball valve element.
A necessary function of this tool is the requirement that the tubing be pressured from the surface to re-open the valve. Pressure above the tool must exceed pressure below the tool before it will open, thus assuring control of the well by a pressure source above the lubricator.